1. Field of the Invention
The present invention relates to a linear motion rolling guide unit performing guidance of relative motion that is used in mechanisms, such as machine tools and industrial robots, that perform relative motion.
2. Description of the Prior Art
An example of this type of linear motion rolling guide unit of the prior art is indicated in FIGS. 1 through 4.
As indicated in FIGS. 1 through 3, said linear motion rolling guide unit is equipped with track rail 2 fixed on bed 1 functioning as the stationary side, and track rail 4 fixed on table 3 functioning as the moving side. A total of 4 of these track rails 2 and 4 are provided in the form of 2 sets with one set consisting of a pair of corresponding rails. Furthermore, there are also cases wherein table 3 is used as the stationary side and bed 1 is used as the moving side.
Bed 1 has projection 1a in its center, with the right and left sides of said projection 1a forming mounting surfaces 1b. The inside surfaces of track rails 2 make contact with mounting surfaces 1b. Mounting surfaces 1c are formed near the right and left sides of the above-mentioned projection 1a, and mounting surfaces 2a formed in the bottom of track rails 2 make contact with these mounting surfaces 1c.
Track surfaces 2b, having roughly V-shaped cross-sections, are formed along the lengthwise direction on the outside of track rails 2. As indicated in FIG. 4, said track surfaces 2b have two flat bearing surfaces 2c mutually intersecting at an angle of, for example, 90 degrees. As is particularly clear from FIG. 4, countersunk portions 2e and threaded insertion holes 2f are concentrically formed extending perpendicular to center line 2d of the angle formed by the above-mentioned track surfaces 2b. The head and threaded portion of a fastening member in the form of bolts 6 (with hexagonal sockets) are inserted into countersunk portions 2e and threaded insertion holes 2f, respectively. These bolts 6 are screwed into bed 1 resulting in track rail 2 being fastened to bed 1. Furthermore, countersunk portions 2e are formed in the uppermost side of track rails 2.
On the other hand, in FIGS. 2 and 3, the other track rails 4, which form pairs with the above-mentioned track rails 2, are attached to table 3 in the manner described below.
In other words, hanging portions 3a are formed on the right and left sides of table 3, and the inside surfaces of each of said hanging portions 3a serve as mounting surfaces 3b. The outside surfaces of track rails 4 then make contact with these mounting surfaces 3b. Mounting surfaces 3c are also formed on the inside of each of the above-mentioned hanging portions 3a on table 3, and mounting surfaces 4a formed on track rails 4 make contact with these mounting surfaces 3c.
V-shaped cross-sectional track surfaces 4b, having two intersecting flat bearing surfaces (not provided with reference numerals) are formed along the lengthwise direction on the insides of track rails 4 in the same manner as track surfaces 2b of the above-mentioned track rails 2. These track rails 4 and the above-mentioned track rails 2 are arranged so that the respective track surfaces 2b and 4b of each of these oppose each other. Furthermore, as indicated in FIGS. 1 and 2, threaded holes 4c are formed in track rails 4, and said track rails 4 are fastened to table 3 by bolts (with hexagonal sockets) 7 that are screwed into said threaded holes 4c.
As indicated in FIGS. 1 and 2, a plurality of rollers 8, and roughly rectangular plate-shaped cage 9, which hold each of said rollers 8 while allowing them to rotate freely, are juxtaposed between the above-mentioned track surfaces 2b and 4b. Each of rollers 8 is arranged in a row so that the central axes of rotation of adjacent rollers mutually cross. Said rollers then roll over each of the above-mentioned track surfaces 2b and 4b.
Furthermore, as indicated in FIGS. 1 and 2, end locking plates 10 and end screws 11 are mounted on the ends of each of track rails 2 and 4 to prevent the above-mentioned cage 9 and rollers 8 from coming out. In addition, as indicated in the same drawings, pre-loading adjustment screw 12, that engages with track rail 4, is screwed into one of the hanging portions 3a of table 3.
As indicated in FIG. 4, in the case of the above-mentioned linear motion rolling guide unit of the prior art, strain forms in the upper portion of track rail 2 as indicated by the double broken line and the opening angle of track surfaces 2b narrows as a result of tightening bolts 6. Thus, said linear motion rolling guide unit of the prior art has the disadvantage of poor operating accuracy and sliding resistance.